62 CARBONIFEROUS LAMELLIBRANCHIATA. 



Observations. — Tlie original type of M'Coy's species has unfortunately com- 

 pletely disappeared, but the specimens which I refer to the same name now have 

 a very close resemblance to the original figure. Little can be made out from 

 M'Coy's description, which is self-contradictory and meagre. It is as follows : — 

 " Transversely ovate, gibbous, beaks small, subterminal. Anterior lobe exceeding 

 half the length of the shell, defined by a strong sulcus from the beali. Hinge-line two- 

 thirds the length of the shell, angulated." The italics are mine. The figure 

 does not show such an anterior lobe as here described, but apart from this curious 

 inaccuracy, the description tallies well with the shells now described, with the 

 exception that the Northumbrian specimens are much larger. This shell appears 

 to be a true Modiola, having the groove for the internal ligament, and a rounded, 

 non-striate hinge-margin, thus differing from Naiadites, to which genus it has a 

 very great superficial resemblance ; indeed, it would be impossible to separate it 

 from this genus, except from the hinge and internal characters, and the associated 

 fossils. The general shape at once separates it from Myalina. M'Coy says in 

 his remarks, " This is one of the very few instances in which the true anteriorly 

 lobed, recent and Oolitic form of Modiola has been found in the older rocks." 



Fortunately the slab of limestone obtained by Mr. John Dunn, of Redesdale, 

 from the Coombs Quarry contains four specimens : one, an imperfect interior, 

 PI. II, fig. 8, happily just giving enough detail of the hinge-structure for 

 correct generic identification ; one, a good cast, PL II, fig. 7, imperfect at 

 the anterior end; and two specimens, PI. II, figs. 5 and 6, of left valves 

 showing surface markings and general shape, while another specimen, PI. II, 

 fig. 9, shows the anterior end. An undoubtedly marine fauna is contained in 

 this bed of limestone. The Irish locality is not given in M'Coy's work, and I am 

 not at present aware of the occurrence of this species anywhere else in Great 

 Britain. 



The example from Foynes Island, figured by Baily but not fully described, 

 named Myalina Foynesiana, is of the same species as the Northumbrian shells. 

 There are two examples on the same slab, — one, the cast of two valves, lying flat 

 open ; the other, the interior of the shell. The striated hinge-plate and terminal 

 umbones of Myalina are conspicuously absent, so that the shell was incorrectly 

 referred to that genus. The anterior end is incomplete, but the casts of the 

 umbones are preserved, and have not the two processes representing the pit-scars 

 of Naiadites on them. The posterior adductor scar is very finely shown in this 

 specimen, PI. II, fig. 10, which I am able to figure by the kind permission of the 

 Director-General of the Geological Survey, Sir A. Geikie. The specimen is in the 

 Collection of the Irish Geological Survey. This shell is associated in the shales 

 with Aviculopecten, Posidonomya, and Goniatites. 



